Polymer Pen Lithography

ABSTRACT

The disclosure relates to methods of printing indicia on a substrate using a tip array comprised of elastomeric, compressible polymers. The tip array can be prepared using conventional photolithographic methods and can be tailored to have any desired number and/or arrangement of tips. Numerous copies (e.g., greater than 15,000, or greater than 11 million) of a pattern can be made in a parallel fashion in as little as 40 minutes.

STATEMENT OF GOVERNMENTAL INTEREST

This invention was made with government support under U54 CA119341awarded by the National Institutes of Health, and EEC0647560 awarded bythe National Science Foundation. The government has certain rights inthe invention.

BACKGROUND

Lithography is used in many areas of modern science and technology,including the production of integrated circuits, information storagedevices, video screens, micro-electromechanical systems (MEMS),miniaturized sensors, microfluidic devices, biochips, photonic bandgapstructures, and diffractive optical elements (1-6). Generally,lithography can be divided into two categories based on patterningstrategy: parallel replication and serial writing. Parallel replicationmethods such as photolithography (7), contact printing (8-11), andnanoimprint lithography (12) are useful for high throughput, large areapatterning. However, most of these methods can only duplicate patterns,which are predefined by serial writing approaches and thus cannot beused to arbitrarily generate different patterns (i.e. one mask leads toone set of structures). In contrast, serial writing methods, includingelectron-beam lithography (EBL), ion beam lithography, and many scanningprobe microscopy (SPM)-based methods (13-16), can create patterns withhigh resolution and registration, but are limited in throughput (17,18). Indeed, only recently have researchers determined ways to usetwo-dimensional cantilever arrays for Dip-Pen Nanolithography (DPN) toproduce patterned structures made of molecule-based materials oversquare centimeter areas (19, 20).

DPN uses an “ink”-coated atomic force microscope (AFM) cantilever todeliver soft or hard materials to a surface with high registration andsub-50-nm resolution in a “constructive” manner (3,16, 21-23). Whencombined with high density cantilever arrays, DPN is a versatile andpowerful tool for constructing molecule-based patterns over relativelylarge areas with moderate throughput (1). The limitations of DPN are: 1)the inability to easily and rapidly work across the micro and nanometerlength scales in a single experiment (typically, either sharp tips areoptimized to generate nanoscale features or blunt tips are used togenerate microscale features) (24); and 2) the need for fragile andcostly two-dimensional cantilever arrays to achieve large areapatterning. Indeed, no simple strategy exists that allows one to rapidlypattern molecule-based features with sizes ranging from the nanometer tomillimeter scale in a parallel, high throughput, and direct-writemanner. Thus, a need exists for lithography methods that can yield ahigh resolution, registration and throughput, soft-matter compatible,and low cost patterning capability.

SUMMARY

The present disclosure is directed to methods of printing indicia on asubstrate surface using a polymer tip array. More specifically,disclosed herein are methods of printing indicia on a substrate surfaceusing a tip array comprising a compressible polymer comprising aplurality of non-cantilevered tips each having a radius of curvature ofless than about 1 μm.

Thus, in one aspect, provided herein is a method of printing indicia ona substrate surface comprising (1) coating a tip array with a patterningcomposition, the tip array comprising a compressible elastomeric polymerhaving a plurality of tips each having a radius of curvature of lessthan about 1 μm, (2) contacting the substrate surface for a firstcontacting period of time and first contacting pressure with all orsubstantially all of the coated tips of the array and thereby depositingthe patterning composition onto the substrate surface to form indiciahaving a substantially uniform feature size of less than 1 μm, andpreferably also a substantially uniform feature shape. The coating cancomprise adsorbing or absorbing the patterning composition onto the tiparray. The method can further comprise moving only one of the tip arrayor the substrate surface, or moving both the tip array and the substratesurface and repeating the contacting step for a second contacting periodof time and second contacting pressure. The first and second contactingperiods of time and pressures can be the same or different. Thecontacting pressure can be controlled by controlling the z-piezo of apiezo scanner upon which the substrate or tip array is mounted. Thelateral movement between the tip array and the substrate surface can becontrolled (e.g., by varying movement and/or limiting movement) to formindicia comprising dots, lines (e.g., straight or curved, formed fromindividual dots or continuously), a preselected pattern, or anycombination thereof. Controlling the contacting pressure and/orcontacting period of time can produce indicia, e.g. dots, having acontrollable, reproducible size. The indicia formed by the methodsdisclosed can have a minimum feature size (e.g., dot size or line width)less than a micron, for example 900 nm or less, 800 nm or less, 700 nmor less, 600 nm or less, 500 nm or less, 400 nm or less, 300 nm or less,200 nm or less, 100 nm or less, 100 nm or less, or 80 nm or less.

Another aspect of the disclosure provides methods of leveling a tiparray disclosed herein with respect to a substrate surface.

One method includes backlighting the tip array with incident light tocause internal reflection of the incident light from the internalsurfaces of the tips, bringing the tips of the tip array and thesubstrate surface together along a z-axis up to a point of contactbetween a subset of the tips with the substrate surface, contactindicated by increased intensity of reflected light from the subset oftips in contact with the substrate surface, whereas no change in theintensity of reflected light from other tips indicates non-contactingtips, and tilting one or both of the tip array and the substrate surfacewith respect to the other in response to differences in intensity of thereflected light from the internal surfaces of the tips, to achievecontact between the substrate surface and non-contacting tips. Thetilting can be performed one or more times and along any one of the x-,y-, and z-axes, to level the array of tips with respect to the substratesurface. The reflected light can be observed by transmission of at leasta portion of the reflected light back through the tip array material inthe direction of the incident light, if the tip array material is atleast translucent. Preferably any substrate to which the tip array ismounted will also be at least translucent or transparent.

Another method includes backlighting the tip array with incident lightto cause internal reflection of the incident light from the internalsurfaces of the tips, bringing the tips of the tip array and thesubstrate surface together along a z-axis to cause contact between thetips of the tip array and the substrate surface, further moving one orboth of the tip array and the substrate towards the other along thez-axis to compress a subset of the tips, whereby the intensity of thereflected light from the tips increases as a function of the degree ofcompression of the tips against the substrate surface, and tilting oneor both of the tip array and the substrate surface with respect to theother in response to differences in intensity of the reflected lightfrom internal surfaces of the tips, to achieve substantially uniformcontact between the substrate surface and tips. The tilting can beperformed one or more times and along any one of the x-, y-, and z-axes,to level the array of tips with respect to the substrate surface, e.g.as determined by uniform intensity of reflected light from the tips. Thereflected light can be observed by transmission of at least a portion ofthe reflected light back through the tip array material in the directionof the incident light, if the tip array material is at leasttranslucent. Preferably any substrate to which the tip array is mountedwill also be at least translucent or transparent.

Another aspect of the present disclosure provides a tip array. The tiparray can comprise a plurality of tips arranged in a regular periodicpattern. The radius of curvature of the tips can be less than about 0.5μm, less than about 0.2 μm, or less than about 100 nm. The tips can beidentically shaped, and can be pyramidal. The polymer of the tip arraycan have a compression modulus of about 10 MPa to about 300 MPa. Thepolymer can be Hookean under pressures of about 10 MPa to about 300 MPa.The polymer can be crosslinked. The polymer can comprisepolydimethylsiloxane (PDMS). The PDMS can be trimethylsiloxy terminatedvinylmethylsiloxane-dimethylsiloxane copolymer, amethylhydrosiloxane-dimethylsiloxane copolymer, or a mixture thereof.The tip array can be fixed to a common substrate. The common substratecan comprise a rigid support, such as glass. Alternatively, the commonsubstrate can be adhered to a rigid support. The common substrate cancomprise an elastomeric layer which can comprise the same polymer asthat of the tip array, or can be a different elastomeric polymer fromthe tip array. The tip array, common substrate, and/or rigid support canbe at least translucent, and can be transparent. In a specificembodiment, the tip array, common substrate, and rigid support, whenpresent, are each at least translucent or transparent. The tip array andcommon substrate (e.g., elastomeric layer) can have a height of lessthan about 200 μm, preferably less than about 150 μm, or more preferablyabout 100 μm.

Yet another aspect of the present disclosure provides a method of makinga tip array, as disclosed herein. The method comprises forming a mastercomprising an array of recesses in a substrate separated by lands;filling the recesses and covering the lands with a prepolymer mixturecomprising a prepolymer and optionally a crosslinker; curing theprepolymer mixture to form a polymer structure; and separating thepolymer structure from the master. The method can further compriseforming the recesses as pyramidal recesses by forming the wells in thesubstrate and anisotropically wet-etching the substrate. The method canfurther comprise covering the filled and coated substrate with a planarglass layer prior to curing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A A schematic illustration of the Polymer Pen Lithography setup.

FIG. 1B A photograph of a 11 million pen array.

FIG. 1C SEM image of the polymer pen array. The average tip radius ofcurvature is 70±10 nm (inset).

FIG. 2A Optical image of a 480 μm×360 μm section of a one million golddot array (6×6 within each block) on a silicon substrate (using a penarray with 28,000 pyramid-shaped tips).

FIG. 2B MHA dot size as a function of relative z-piezo extension. Theresults were obtained using a polymer pen array with 15,000pyramid-shaped tips at 25° C. with a relative humidity of 40%.

FIG. 2C Optical image of arrays of gold squares generated at differentz-piezo extensions (using a pen array with 28,000 pyramid-shaped tips).

FIG. 2D An optical microscope image of a multi-dimensional gold circuitfabricated by Polymer Pen Lithography. The inset shows a magnified imageof the circuit center.

FIG. 3.A SEM image of a representative region of approximately 15,000miniaturized duplicates of the 2008 Beijing Olympic logo.

FIG. 3B A zoom-in optical image of a representative replica. The insetshows a magnified SEM image of the letter “e”.

FIG. 4A SEM image of a polymer pen array with a glass support. Thepolymer pen array with a glass support is uniform across the whole area.

FIG. 4B SEM image of a polymer pen array without a glass support showingthat the polymer pen array without a glass support is wavy.

FIG. 5A A photograph of an etched gold pattern on a 4 inch Si waferfabricated by Polymer Pen Lithography using the 11-million pen arrayshown in FIG. 1B. The area patterned by the pen array is highlightedwith a white dashed line. In the center of the pen array, greater than99% of the pens uniformly deliver the MHA ink to the substrate duringthe Polymer Pen Lithography process and form well-defined structures.Reduced activity occurs on the periphery of the array, due to poorcontact between the pens in the peripheral area of the array and the Sisubstrate. This arises from current instrument sample holderlimitations.

FIG. 5B Optical microscope image of gold patterns in FIG. 5A made byPolymer Pen Lithography. The inset is a zoom-in image. The image showsthat every intended structure forms in this experiment.

FIG. 6. MHA dot size as a function of tip-substrate contact time. Dotsize increases with increasing tip-substrate contact time at constantcontact (pressure) (initial contact). The results were obtained using apolymer pen array with 15,000 pyramid-shaped tips at a temperature of23° C. and relative humidity of 50% (circles) and 90% (squares).

FIG. 7. Fluorescence microscopy image of Anti-Mouse IgG arraysfabricated by Polymer Pen Lithography.

FIG. 8. A schematic illustration of the set up of tip array, piezoscanner, and substrate surface, in relation to a light source, used forleveling the tip array with respect to the substrate surface.

DETAILED DESCRIPTION

Polymer Pen Lithography is a direct-write method that deliverscollections of molecules in a positive printing mode. In contrast withDPN and other SPM-based lithographies, which typically use hardsilicon-based cantilevers, Polymer Pen Lithography utilizes elastomerictips without cantilevers (25, 26) as the ink delivery tool. The tips arepreferably made of polydimethylsiloxane, PDMS. A preferred polymer penarray (FIG. 1A) contains thousands of tips, preferably having apyramidal shape, which can be made with a master prepared byconventional photolithography and subsequent wet chemical etching (FIG.1A). The tips preferably are connected by a common substrate whichincludes a thin polymer backing layer (50-100 μm thick), whichpreferably is adhered to a rigid support (e.g., a glass, silicon,quartz, ceramic, polymer, or any combination thereof), e.g. prior to orvia curing of the polymer. The rigid support is preferably highly rigidand has a highly planar surface upon which to mount the array (e.g.,silica glass, quartz, and the like). The rigid support and thin backinglayer significantly improve the uniformity of the polymer pen array overlarge areas, such as three inch wafer surface (FIG. 1B, 4A), and makepossible the leveling and uniform, controlled use of the array. When thesharp tips of the polymer pens are brought in contact with a substrate,ink is delivered at the points of contact (FIG. 1A).

The amount of light reflected from the internal surfaces of the tipsincreases significantly when the tips make contact with the substrate.Therefore, a translucent or transparent elastomer polymer pen arrayallows one to visually determine when all of the tips are in contactwith an underlying substrate, permitting one to address the otherwisedaunting task of leveling the array in an experimentally straightforwardmanner. Thus, preferably one or more of the array tips, backing layer,and rigid support are at least translucent, and preferably transparent.

Polymer Pen Lithography experiments were performed with an Nscriptor™system (NanoInk Inc., IL) equipped with a 90-μm closed loop scanner andcommercial lithography software (DPNWrite™, DPN System-2, NanoInk Inc.,IL). Depending upon intended use, the pitch of a pen array isdeliberately set between 20 μm and 1 mm, corresponding to pen densitiesof 250,000/cm² and 100/cm², respectively. Larger pitch arrays arerequired to make large features (micron or millimeter scale) but alsocan be used to make nanometer scale features. All of the pens wereremarkably uniform in size and shape, with an average tip radius of70±10 nm (FIG. 1C). In principle, this value could be reducedsubstantially with higher quality masters and stiffer elastomers. Forthe examples below, the tip array used contained either 15,000 or 28,000pyramid-shaped pens, but arrays with as many as about 11,000,000 penshave also been used to pattern structures (FIG. 5).

In a typical experiment, a pen array (1 cm² in size) was inked byimmersing it in a saturated solution of 16-mercaptohexadecanoic acid(MHA) in ethanol for five minutes followed by rinsing with ethanol. Theinked pen array was used for generating 1-μm diameter MHA dot patternson a thermally evaporated polycrystalline gold substrate (25 nm Au witha 5 nm Ti adhesion layer coated on Si) by bringing it in contact withthe gold surface for 0.1 s. This process of contacting the goldsubstrate was repeated 35 times to generate a 6×6 array of MHA dots(less than 10% deviation in feature diameter). The exposed gold on thisMHA patterned substrate was subsequently etched (20 mM thiourea, 30 mMiron nitrate, 20 mM hydrochloric acid, and 2 mM octanol in water) toyield raised structures that are approximately 25 nm in height andeasily imaged by optical microscopy (FIG. 2A).

A defining characteristic of Polymer Pen Lithography, in contrast withDPN and most contact printing strategies which are typically viewed aspressure or force-independent (21), is that it exhibits both time- andpressure-dependent ink transport. As with DPN, features made by PolymerPen Lithography exhibit a size that is linearly dependent on the squareroot of the tip-substrate contact time (FIG. 6) (27, 28). This propertyof Polymer Pen Lithography, which is a result of the diffusivecharacteristics of the ink and the small size of the delivery tips,allows one to pattern sub-micron features with high precision andreproducibility (variation of feature size is less than 10% under thesame experimental conditions). The pressure dependence of Polymer PenLithography derives from the compressible nature of the elastomerpyramid array. Indeed, the microscopic, preferably pyramidal, tips canbe made to deform with successively increasing amounts of appliedpressure, which can be controlled by simply extending the piezo in thevertical direction (z-piezo). Although such deformation has beenregarded as a major drawback in contact printing (it can result in“roof” collapse and limit feature size resolution), with Polymer PenLithography, the controlled deformation can be used as an adjustablevariable, allowing one to control tip-substrate contact area andresulting feature size. Within the pressure range allowed by z-piezoextension of about 5 to about 25 μm, one can observe a near linearrelationship between piezo extension and feature size at a fixed contacttime of 1 s (FIG. 2B). Interestingly, at the point of initial contactand up to a relative extension 0.5 μm, the sizes of the MHA dots do notsignificantly differ and are both about 500 nm, indicating that thebacking elastomer layer, which connects all of the pyramids, deformsbefore the pyramid-shaped tips do. This type of buffering is fortuitousand essential for leveling because it provides extra tolerance inbringing all of the tips in contact with the surface without tipdeformation and significantly changing the intended feature size. Whenthe z-piezo extends 1 μm or more, the tips exhibit a significant andcontrollable deformation (FIG. 2B).

With the pressure dependency of Polymer Pen Lithography, one does nothave to rely on the time-consuming, meniscus-mediated ink diffusionprocess to generate large features. Indeed, one can generate eithernanometer or micrometer sized features in only one printing cycle bysimply adjusting the degree of tip deformation. As proof-of-concept, 6×6gold square arrays, where each square in a row was written with oneprinting cycle at different tip-substrate pressures but a constant 1 stip-substrate contact time, were fabricated by Polymer Pen Lithographyand subsequent wet chemical etching (FIG. 2C). The largest and smallestgold squares are 4 μm and 600 nm on edge, respectively. Note that thisexperiment does not define the feature size range attainable in aPolymer Pen Lithography experiment, but rather, is a demonstration ofthe multiple scales accessible by Polymer Pen Lithography at a fixedtip-substrate contact time (1 s in this case).

Polymer Pen Lithography, unlike conventional contact printing, allowsfor the combinatorial patterning of molecule-based and solid-statefeatures with dynamic control over feature size, spacing, and shape.This is accomplished by using the polymer tips to form a dot pattern ofthe structure one wants to make. As proof-of-concept, a polymer penarray with 100 pyramidal tips spaced 1 mm apart was used to generate 100duplicates of an integrated gold circuit. The width of each electrode inthe center of the circuit is 500 nm, while the width of each electrodelead going to these nanometer scale electrodes is 10 μm, and the size ofthe external bonding pad is a 100×100 μm² (FIG. 2D). Since theNscriptor™ only provides a 90×90 μm² scanner, the circuits were dividedinto 35 80×80 μm² sub-patterns, which were stitched together by manuallymoving the stage motor after each sub-pattern was generated. Thislimitation could be addressed by programming the movement of the stagemotor relative to the positions of the multiple sub-patterns. Toaccommodate both the resolution and throughput concerns, differentrelative z-piezo extensions at different positions of the circuit wereused, where 0 (initial contact), 2, and 6 μm were used for the centralelectrodes, electrode leads, and bonding pads, respectively. As aresult, writing a 100×100 μm² area only requires 400 printing cycles(less than 0.5 s for each cycle), and the total time required togenerate 100 duplicates of the circuit took approximately 2 hr.Re-inking of the pen array is not necessary because the PDMS polymerbehaves as a reservoir for the ink throughout the experiment (27, 28).This relatively high-throughput production of multiscale patterns wouldbe difficult, if not impossible, to do by EBL or DPN.

Note that the maskless nature of Polymer Pen Lithography allows one toarbitrarily make many types of structures without the hurdle ofdesigning a new master via a throughput-impeded serial process. Inaddition, Polymer Pen Lithography can be used with sub-100 nm resolutionwith the registration capabilities of a closed-loop scanner. Forexample, Polymer Pen Lithography was used to generate 15,000 replicas ofthe 2008 Beijing Olympic logo on gold with MHA as the ink and subsequentwet chemical etching (FIG. 3A). Each logo was generated using themultiscale capabilities of Polymer Pen Lithography from a 70×60 μm²bitmap. The letters and numbers, “Beijing 2008”, were generated from˜20,000 90-nm dots (initial contact), while the picture and Olympicrings were made from ˜4,000 600-nm dots at higher array-substratecontact pressures (relative piezo extension=1 μm). These structures werecreated by holding the pen array at each spot for 0.05 s and travelingbetween spots at a speed of 60 μm/s. A representative portion of theapproximately 15,000 replicas (yield >99%) generated across the 1 cm²substrate shows their uniformity (FIG. 3B). The total time required tofabricate all of these structures was less than 40 min.

A new lithography method, termed Polymer Pen Lithography, has beendeveloped using elastomeric pen arrays mounted on an inscripting device,such as an Nscriptor™ instrument, to generate nano- and microscalefeatures in a constructive manner. The technique merges many of theattributes of DPN and contact printing to yield patterning capabilitiesthat span multiple length scales with high throughput and low cost. Thenovel time- and pressure-dependent ink transport properties of thepolymer pen pyramid arrays provide important and tunable variables thatdistinguish Polymer Pen Lithography from the many nano- andmicrofabrication approaches that have been developed to date. SincePolymer Pen Lithography is a direct-write technique, it is also usefulfor fabricating arrays of structures made of soft matter, such asproteins (FIG. 7), making it useful in the life sciences as well.

Tip Arrays

The lithography methods disclosed herein employ a tip array formed fromelastomeric polymer material. The tip arrays are non-cantilevered andcomprise tips which can be designed to have any shape or spacing betweenthem, as needed. The shape of each tip can be the same or different fromother tips of the array. Contemplated tip shapes include spheroid,hemispheroid, toroid, polyhedron, cone, cylinder, and pyramid (trigonalor square). The tips are sharp, so that they are suitable for formingsubmicron patterns, e.g., less than about 500 nm. The sharpness of thetip is measured by its radius of curvature, and the radius of curvatureof the tips disclosed herein is below 1 μm, and can be less than about0.9 μm, less than about 0.8 μm, less than about 0.7 μm, less than about0.6 μm, less than about 0.5 μm, less than about 0.4 μm, less than about0.3 μm, less than about 0.2 μm, less than about 0.1 μm, less than about90 nm, less than about 80 nm, less than about 70 nm, less than about 60nm, or less than about 50 nm.

The tip array can be formed from a mold made using photolithographymethods, which is then used to fashion the tip array using a polymer asdisclosed herein. The mold can be engineered to contain as many tipsarrayed in any fashion desired. The tips of the tip array can be anynumber desired, and contemplated numbers of tips include about 1000 tipsto about 15 million tips, or greater. The number of tips of the tiparray can be greater than about 1 million, greater than about 2 million,greater than about 3 million, greater than about 4 million, greater than5 million tips, greater than 6 million, greater than 7 million, greaterthan 8 million, greater than 9 million, greater than 10 million, greaterthan 11 million, greater than 12 million, greater than 13 million,greater than 14 million, or greater than 15 million tips.

The tips of the tip array can be designed to have any desired thickness,but typically the thickness of the tip array is about 50 nm to about 1μm, about 50 nm to about 500 nm, about 50 nm to about 400 nm, about 50nm to about 300 nm, about 50 nm to about 200 nm, or about 50 nm to about100 nm.

The polymers can be any polymer having a compressibility compatible withthe lithographic methods. Polymeric materials suitable for use in thetip array can have linear or branched backbones, and can be crosslinkedor non-crosslinked, depending upon the particular polymer and the degreeof compressibility desired for the tip. Cross-linkers refer tomulti-functional monomers capable of forming two or more covalent bondsbetween polymer molecules. Non-limiting examples of cross-linkersinclude such as trimethylolpropane trimethacrylate (TMPTMA),divinylbenzene, di-epoxies, tri-epoxies, tetra-epoxies, di-vinyl ethers,tri-vinyl ethers, tetra-vinyl ethers, and combinations thereof.

Thermoplastic or thermosetting polymers can be used, as can crosslinkedelastomers. In general, the polymers can be porous and/or amorphous. Avariety of elastomeric polymeric materials are contemplated, includingpolymers of the general classes of silicone polymers and epoxy polymers.Polymers having low glass transition temperatures such as, for example,below 25° C. or more preferably below −50° C., can be used. Diglycidylethers of bisphenol A can be used, in addition to compounds based onaromatic amine, triazine, and cycloaliphatic backbones. Another exampleincludes Novolac polymers. Other contemplated elastomeric polymersinclude methylchlorosilanes, ethylchlorosilanes, andphenylchlorosilanes, polydimethylsiloxane (PDMS). Other materialsinclude polyethylene, polystyrene, polybutadiene, polyurethane,polyisoprene, polyacrylic rubber, fluorosilicone rubber, andfluoroelastomers.

Further examples of suitable polymers that may be used to form a tip canbe found in U.S. Pat. Nos. 5,776,748; 6,596,346; and 6,500,549, each ofwhich is hereby incorporated by reference in its entirety. Othersuitable polymers include those disclosed by He et al., Langmuir 2003,19, 6982-6986; Donzel et al., Adv. Mater. 2001, 13, 1164-1167; andMartin et al., Langmuir, 1998, 14-15, 3791-3795. Hydrophobic polymerssuch as polydimethylsiloxane can be modified either chemically orphysically by, for example, exposure to a solution of a strong oxidizeror to an oxygen plasma.

The polymer of the tip array has a suitable compression modulus andsurface hardness to prevent collapse of the polymer during inking andprinting, but too high a modulus and too great a surface hardness canlead to a brittle material that cannot adapt and conform to a substratesurface during printing. As disclosed in Schmid, et al., Macromolecules,33:3042 (2000), vinyl and hydrosilane prepolymers can be tailored toprovide polymers of different modulus and surface hardness. Thus, insome cases, the polymer is a mixture of vinyl and hydrosilaneprepolymers, where the weight ratio of vinyl prepolymer to hydrosilanecrosslinker is about 5:1 to about 20:1, about 7:1 to about 15:1, orabout 8:1 to about 12:1.

The polymers of the tip array preferably will have a surface hardness ofabout 0.2% to about 3.5% of glass, as measured by resistance of asurface to penetration by a hard sphere with a diameter of 1 mm,compared to the resistance of a glass surface (as described in Schmid,et al., Macromolecules, 33:3042 (2000) at p 3044). The surface hardnesscan be about 0.3% to about 3.3%, about 0.4% to about 3.2%, about 0.5% toabout 3.0%, or about 0.7% to about 2.7%. The polymers of the tip arraycan have a compression modulus of about 10 MPa to about 300 MPa. The tiparray preferably comprises a compressible polymer which is Hookean underpressures of about 10 MPa to about 300 MPa. The linear relationshipbetween pressure exerted on the tip array and the feature size allowsfor control of the indicia printed using the disclosed methods and tiparrays (see FIG. 2B).

The tip array can comprise a polymer that has adsorption and/orabsorption properties for the patterning composition, such that the tiparray acts as its own patterning composition reservoir. For example,PDMS is known to adsorb patterning inks, see, e.g., US PatentPublication No. 2004/228962, Zhang, et al., Nano Lett. 4, 1649 (2004),and Wang et al., Langmuir 19, 8951 (2003).

The tip array can comprise a plurality of tips fixed to a commonsubstrate and formed from a polymer as disclosed herein. The tips can bearranged randomly or in a regular periodic pattern (e.g., in columns androws, in a circular pattern, or the like). The tips can all have thesame shape or be constructed to have different shapes. The commonsubstrate can comprise an elastomeric layer, which can comprise the samepolymer that forms the tips of the tip array, or can comprise anelastomeric polymer that is different from that of the tip array. Theelastomeric layer can have a thickness of about 50 μm to about 100 μm.The tip array can be affixed or adhered to a rigid support (e.g., glass,such as a glass slide). In various cases, the common substrate, the tiparray, and/or the rigid support, if present, is translucent ortransparent. In a specific case, each is translucent or transparent. Thethickness of combination of the tip array and common substrate, can beless than about 200 μm, preferably less than about 150 μm, or morepreferably about 100 μm.

Patterning Compositions

Patterning compositions suitable for use in the disclosed methodsinclude both homogeneous and heterogeneous compositions, the latterreferring to a composition having more than one component. Thepatterning composition is coated on the tip array. The term “coating,”as used herein, refers both to coating of the tip array as welladsorption and absorption by the tip array of the patterningcomposition. Upon coating of the tip array with the patterningcomposition, the patterning composition can be patterned on a substratesurface using the tip array.

Patterning compositions can be liquids, solids, semi-solids, and thelike. Patterning compositions suitable for use include, but are notlimited to, molecular solutions, polymer solutions, pastes, gels,creams, glues, resins, epoxies, adhesives, metal films, particulates,solders, etchants, and combinations thereof.

Patterning compositions can include materials such as, but not limitedto, monolayer-forming species, thin film-forming species, oils,colloids, metals, metal complexes, metal oxides, ceramics, organicspecies (e.g., moieties comprising a carbon-carbon bond, such as smallmolecules, polymers, polymer precursors, proteins, antibodies, and thelike), polymers (e.g., both non-biological polymers and biologicalpolymers such as single and double stranded DNA, RNA, and the like),polymer precursors, dendrimers, nanoparticles, and combinations thereof.In some embodiments, one or more components of a patterning compositionincludes a functional group suitable for associating with a substrate,for example, by forming a chemical bond, by an ionic interaction, by aVan der Waals interaction, by an electrostatic interaction, bymagnetism, by adhesion, and combinations thereof.

In some embodiments, the composition can be formulated to control itsviscosity. Parameters that can control ink viscosity include, but arenot limited to, solvent composition, solvent concentration, thickenercomposition, thickener concentration, particles size of a component, themolecular weight of a polymeric component, the degree of cross-linkingof a polymeric component, the free volume (i.e., porosity) of acomponent, the swellability of a component, ionic interactions betweenink components (e.g., solvent-thickener interactions), and combinationsthereof.

In some embodiments, the patterning composition comprises an additive,such as a solvent, a thickening agent, an ionic species (e.g., a cation,an anion, a zwitterion, etc.) the concentration of which can be selectedto adjust one or more of the viscosity, the dielectric constant, theconductivity, the tonicity, the density, and the like.

Suitable thickening agents include, but are not limited to, metal saltsof carboxyalkylcellulose derivatives (e.g., sodiumcarboxymethylcellulose), alkylcellulose derivatives (e.g.,methylcellulose and ethylcellulose), partially oxidized alkylcellulosederivatives (e.g., hydroxyethylcellulose, hydroxypropylcellulose andhydroxypropylmethylcellulose), starches, polyacrylamide gels,homopolymers of poly-N-vinylpyrrolidone, poly(alkyl ethers) (e.g.,polyethylene oxide, polyethylene glycol, and polypropylene oxide), agar,agarose, xanthan gums, gelatin, dendrimers, colloidal silicon dioxide,lipids (e.g., fats, oils, steroids, waxes, glycerides of fatty acids,such as oleic, linoleic, linolenic, and arachidonic acid, and lipidbilayers such as from phosphocholine) and combinations thereof. In someembodiments, a thickener is present in a concentration of about 0.5% toabout 25%, about 1% to about 20%, or about 5% to about 15% by weight ofa patterning composition.

Suitable solvents for a patterning composition include, but are notlimited to, water, C1-C8 alcohols (e.g., methanol, ethanol, propanol andbutanol), C6-C12 straight chain, branched and cyclic hydrocarbons (e.g.,hexane and cyclohexane), C6-C14 aryl and aralkyl hydrocarbons (e.g.,benzene and toluene), C3-C10 alkyl ketones (e.g., acetone), C3-C10esters (e.g., ethyl acetate), C4-C10 alkyl ethers, and combinationsthereof. In some embodiments, a solvent is present in a concentration ofabout 1% to about 99%, about 5% to about 95%, about 10% to about 90%,about 15% to about 95%, about 25% to about 95%, about 50% to about 95%,or about 75% to about 95% by weight of a patterning composition.

Patterning compositions can comprise an etchant. As used herein, an“etchant” refers to a component that can react with a surface to removea portion of the surface. Thus, an etchant is used to form a subtractivefeature by reacting with a surface and forming at least one of avolatile and/or soluble material that can be removed from the substrate,or a residue, particulate, or fragment that can be removed from thesubstrate by, for example, a rinsing or cleaning method. In someembodiments, an etchant is present in a concentration of about 0.5% toabout 95%, about 1% to about 90%, about 2% to about 85%, about 0.5% toabout 10%, or about 1% to about 10% by weight of the patterningcomposition.

Etchants suitable for use in the methods disclosed herein include, butare not limited to, an acidic etchant, a basic etchant, a fluoride-basedetchant, and combinations thereof. Acidic etchants suitable for use withthe present invention include, but are not limited to, sulfuric acid,trifluoromethanesulfonic acid, fluorosulfonic acid, trifluoroaceticacid, hydrofluoric acid, hydrochloric acid, carborane acid, andcombinations thereof. Basic etchants suitable for use with the presentinvention include, but are not limited to, sodium hydroxide, potassiumhydroxide, ammonium hydroxide, tetraalkylammonium hydroxide ammonia,ethanolamine, ethylenediamine, and combinations thereof. Fluoride-basedetchants suitable for use with the present invention include, but arenot limited to, ammonium fluoride, lithium fluoride, sodium fluoride,potassium fluoride, rubidium fluoride, cesium fluoride, franciumfluoride, antimony fluoride, calcium fluoride, ammoniumtetrafluoroborate, potassium tetrafluoroborate, and combinationsthereof.

In some embodiments, the patterning composition includes a reactivecomponent. As used herein, a “reactive component” refers to a compoundor species that has a chemical interaction with a substrate. In someembodiments, a reactive component in the ink penetrates or diffuses intothe substrate. In some embodiments, a reactive component transforms,binds, or promotes binding to exposed functional groups on the surfaceof the substrate. Reactive components can include, but are not limitedto, ions, free radicals, metals, acids, bases, metal salts, organicreagents, and combinations thereof. Reactive components further include,without limitation, monolayer-forming species such as thiols,hydroxides, amines, silanols, siloxanes, and the like, and othermonolayer-forming species known to a person or ordinary skill in theart. The reactive component can be present in a concentration of about0.001% to about 100%, about 0.001% to about 50%, about 0.001% to about25%, about 0.001% to about 10%, about 0.001% to about 5%, about 0.001%to about 2%, about 0.001% to about 1%, about 0.001% to about 0.5%, about0.001% to about 0.05%, about 0.01% to about 10%, about 0.01% to about5%, about 0.01% to about 2%, about 0.01% to about 1%, about 10% to about100%, about 50% to about 99%, about 70% to about 95%, about 80% to about99%, about 0.001%, about 0.005%, about 0.01%, about 0.1%, about 0.5%,about 1%, about 2%, or about 5% weight of the patterning composition.

The patterning composition can further comprise a conductive and/orsemi-conductive component. As used herein, a “conductive component”refers to a compound or species that can transfer or move electricalcharge. Conductive and semi-conductive components include, but are notlimited to, a metal, a nanoparticle, a polymer, a cream solder, a resin,and combinations thereof. In some embodiments, a conductive component ispresent in a concentration of about 1% to about 100%, about 1% to about10%, about 5% to about 100%, about 25% to about 100%, about 50% to about100%, about 75% to about 99%, about 2%, about 5%, about 90%, about 95%by weight of the patterning composition.

Metals suitable for use in a patterning composition include, but are notlimited to, a transition metal, aluminum, silicon, phosphorous, gallium,germanium, indium, tin, antimony, lead, bismuth, alloys thereof, andcombinations thereof.

In some embodiments, the patterning composition comprises asemi-conductive polymer. Semi-conductive polymers suitable for use withthe present invention include, but are not limited to, a polyaniline, apoly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), a polypyrrole,an arylene vinylene polymer, a polyphenylenevinylene, a polyacetylene, apolythiophene, a polyimidazole, and combinations thereof.

The patterning composition can include an insulating component. As usedherein, an “insulating component” refers to a compound or species thatis resistant to the movement or transfer of electrical charge. In someembodiments, an insulating component has a dielectric constant of about1.5 to about 8 about 1.7 to about 5, about 1.8 to about 4, about 1.9 toabout 3, about 2 to about 2.7, about 2.1 to about 2.5, about 8 to about90, about 15 to about 85, about 20 to about 80, about 25 to about 75, orabout 30 to about 70. Insulating components suitable for use in themethods disclosed herein include, but are not limited to, a polymer, ametal oxide, a metal carbide, a metal nitride, monomeric precursorsthereof, particles thereof, and combinations thereof. Suitable polymersinclude, but are not limited to, a polydimethylsiloxane, asilsesquioxane, a polyethylene, a polypropylene, a polyimide, andcombinations thereof. In some embodiments, for example, an insulatingcomponent is present in a concentration of about 1% to about 95%, about1% to about 80%, about 1% to about 50%, about 1% to about 20%, about 1%to about 10%, about 20% to about 95%, about 20% to about 90%, about 40%to about 80%, about 1%, about 5%, about 10%, about 90%, or about 95% byweight of the patterning composition.

The patterning composition can include a masking component. As usedherein, a “masking component” refers to a compound or species that uponreacting forms a surface feature resistant to a species capable ofreacting with the surrounding surface. Masking components suitable foruse with the present invention include materials commonly employed intraditional photolithography methods as “resists” (e.g., photoresists,chemical resists, self-assembled monolayers, etc.). Masking componentssuitable for use in the disclosed methods include, but are not limitedto, a polymer such as a polyvinylpyrollidone,poly(epichlorohydrin-co-ethyleneoxide), a polystyrene, apoly(styrene-co-butadiene), a poly(4-vinylpyridine-co-styrene), an amineterminated poly(styrene-co-butadiene), apoly(acrylonitrile-co-butadiene), a styrene-butadiene-styrene blockcopolymer, a styrene-ethylene-butylene block linear copolymer, apolystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene, apoly(styrene-co-maleic anhydride), apolystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene-graft-maleicanhydride, a polystyrene-block-polyisoprene-block-polystyrene, apolystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene, apolynorbornene, a dicarboxy terminatedpoly(acrylonitrile-co-butadiene-co-acrylic acid), a dicarboxy terminatedpoly(acrylonitrile-co-butadiene), a polyethyleneimine, a poly(carbonateurethane), a poly(acrylonitrile-co-butadiene-co-styrene), apoly(vinylchloride), a poly(acrylic acid), a poly(methylmethacrylate), apoly(methyl methacrylate-co-methacrylic acid), a polyisoprene, apoly(1,4-butylene terephthalate), a polypropylene, a poly(vinylalcohol), a poly(1,4-phenylene sulfide), a polylimonene, apoly(vinylalcohol-co-ethylene), apoly[N,N′-(1,3-phenylene)isophthalamide], a poly(1,4-phenyleneether-ether-sulfone), a poly(ethyleneoxide), a poly[butyleneterephthalate-co-poly(alkylene glycol) terephthalate], a poly(ethyleneglycol) diacrylate, a poly(4-vinylpyridine), a poly(DL-lactide), apoly(3,3′,4,4′-benzophenonetetracarboxylicdianhydride-co-4,4′-oxydianiline/1,3-phenylenediamine), an agarose, apolyvinylidene fluoride homopolymer, a styrene butadiene copolymer, aphenolic resin, a ketone resin, a4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxane, a salt thereof, andcombinations thereof. In some embodiments, a masking component ispresent in a concentration of about 1% to about 10%, about 1% to about5%, or about 2% by weight of the patterning composition.

The patterning composition can include a conductive component and areactive component. For example, a reactive component can promote atleast one of: penetration of a conductive component into a surface,reaction between the conductive component and a surface, adhesionbetween a conductive feature and a surface, promoting electrical contactbetween a conductive feature and a surface, and combinations thereof.Surface features formed by reacting this patterning composition includeconductive features selected from the group consisting of: additivenon-penetrating, additive penetrating, subtractive penetrating, andconformal penetrating surface features.

The patterning composition can comprise an etchant and a conductivecomponent, for example, suitable for producing a subtractive surfacefeature having a conductive feature inset therein.

The patterning composition can comprise an insulating component and areactive component. For example, a reactive component can promote atleast one of: penetration of an insulating component into a surface,reaction between the insulating component and a surface, adhesionbetween an insulating feature and a surface, promoting electricalcontact between an insulating feature and a surface, and combinationsthereof. Surface features formed by reacting this patterning compositioninclude insulating features selected from the group consisting of:additive non-penetrating, additive penetrating, subtractive penetrating,and conformal penetrating surface features.

The patterning composition can comprise an etchant and an insulatingcomponent, for example, suitable for producing a subtractive surfacefeature having an insulating feature inset therein.

The patterning composition can comprise a conductive component and amasking component, for example, suitable for producing electricallyconductive masking features on a surface.

Other contemplated components of a patterning composition suitable foruse with the disclosed methods include thiols, 1,9-Nonanedithiolsolution, silane, silazanes, alkynes cystamine, N-Fmoc protected aminothiols, biomolecules, DNA, proteins, antibodies, collagen, peptides,biotin, and carbon nanotubes.

For a description of patterning compounds and patterning compositions,and their preparation and use, see Xia and Whitesides, Angew. Chem. Int.Ed., 37, 550-575 (1998) and references cited therein; Bishop et al.,Curr. Opinion Colloid & Interface Sci., 1, 127-136 (1996); Calvert, J.Vac. Sci. Technol. B, 11, 2155-2163 (1993); Ulman, Chem. Rev., 96:1533(1996) (alkanethiols on gold); Dubois et al., Annu. Rev. Phys. Chem.,43:437 (1992) (alkanethiols on gold); Ulman, An Introduction toUltrathin Organic Films: From Langmuir-Blodgett to Self-Assembly(Academic, Boston, 1991) (alkanethiols on gold); Whitesides, Proceedingsof the Robert A. Welch Foundation 39th Conference On Chemical ResearchNanophase Chemistry, Houston, Tex., pages 109-121 (1995) (alkanethiolsattached to gold); Mucic et al. Chem. Commun. 555-557 (1996) (describesa method of attaching 3′ thiol DNA to gold surfaces); U.S. Pat. No.5,472,881 (binding of oligonucleotide-phosphorothiolates to goldsurfaces); Burwell, Chemical Technology, 4, 370-377 (1974) and Matteucciand Caruthers, J. Am. Chem. Soc., 103, 3185-3191 (1981) (binding ofoligonucleotides-alkylsiloxanes to silica and glass surfaces); Grabar etal., Anal. Chem., 67, 735-743 (binding of aminoalkylsiloxanes and forsimilar binding of mercaptoalkylsiloxanes); Nuzzo et al., J. Am. Chem.Soc., 109, 2358 (1987) (disulfides on gold); Allara and Nuzzo, Langmuir,1, 45 (1985) (carboxylic acids on aluminum); Allara and Tompkins, J.Colloid Interfate Sci., 49, 410-421 (1974) (carboxylic acids on copper);Iler, The Chemistry Of Silica, Chapter 6, (Wiley 1979) (carboxylic acidson silica); Timmons and Zisman, J. Phys. Chem., 69, 984-990 (1965)(carboxylic acids on platinum); Soriaga and Hubbard, J. Am. Chem. Soc.,104, 3937 (1982) (aromatic ring compounds on platinum); Hubbard, Acc.Chem. Res., 13, 177 (1980) (sulfolanes, sulfoxides and otherfunctionalized solvents on platinum); Hickman et al., J. Am. Chem. Soc.,111, 7271 (1989) (isonitriles on platinum); Maoz and Sagiv, Langmuir, 3,1045 (1987) (silanes on silica); Maoz and Sagiv, Langmuir, 3, 1034(1987) (silanes on silica); Wasserman et al., Langmuir, 5, 1074 (1989)(silanes on silica); Eltekova and Eltekov, Langmuir, 3,951 (1987)(aromatic carboxylic acids, aldehydes, alcohols and methoxy groups ontitanium dioxide and silica); and Lec et al., J. Phys. Chem., 92, 2597(1988) (rigid phosphates on metals); Lo et al., J. Am. Chem. Soc., 118,11295-11296 (1996) (attachment of pyrroles to superconductors); Chen etal., J. Am. Chem. Soc., 117, 6374-5 (1995) (attachment of amines andthiols to superconductors); Chen et al., Langmuir, 12, 2622-2624 (1996)(attachment of thiols to superconductors); McDevitt et al., U.S. Pat.No. 5,846,909 (attachment of amines and thiols to superconductors); Xuet al., Langmuir, 14, 6505-6511 (1998) (attachment of amines tosuperconductors); Mirkin et al., Adv. Mater. (Weinheim, Ger.), 9,167-173 (1997) (attachment of amines to superconductors); Hovis et al.,J. Phys. Chem. B, 102, 6873-6879 (1998) (attachment of olefins anddienes to silicon); Hovis et al., Surf. Sci., 402-404, 1-7 (1998)(attachment of olefins and dienes to silicon); Hovis et al., J. Phys.Chem. B, 101, 9581-9585 (1997) (attachment of olefins and dienes tosilicon); Hamers et al., J. Phys. Chem. B, 101, 1489-1492 (1997)(attachment of olefins and dienes to silicon); Hamers et al., U.S. Pat.No. 5,908,692 (attachment of olefins and dienes to silicon); Ellison etal., J. Phys. Chem. B, 103, 6243-6251 (1999) (attachment ofisothiocyanates to silicon); Ellison et al., J. Phys. Chem. B, 102,8510-8518 (1998) (attachment of azoalkanes to silicon); Ohno et al.,Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A, 295, 487-490 (1997)(attachment of thiols to GaAs); Reuter et al., Mater. Res. Soc. Symp.Proc., 380, 119-24 (1995) (attachment of thiols to GaAs); Bain, Adv.Mater. (Weinheim, Fed. Repub. Ger.), 4, 591-4 (1992) (attachment ofthiols to GaAs); Sheen et al., J. Am. Chem. Soc., 114, 1514-15 (1992)(attachment of thiols to GaAs); Nakagawa et al., Jpn. J. Appl. Phys.,Part 1, 30, 3759-62 (1991) (attachment of thiols to GaAs); Lunt et al.,J. Appl. Phys., 70, 7449-67 (1991) (attachment of thiols to GaAs); Luntet al., J. Vac. Sci. Technol., B, 9, 2333-6 (1991) (attachment of thiolsto GaAs); Yamamoto et al., Langmuir ACS ASAP, web release numberIa990467r (attachment of thiols to InP); Gu et al., J. Phys. Chem. B,102, 9015-9028 (1998) (attachment of thiols to InP); Menzel et al., Adv.Mater. (Weinheim, Ger.), 11, 131-134 (1999) (attachment of disulfides togold); Yonezawa et al., Chem. Mater., 11, 33-35 (1999) (attachment ofdisulfides to gold); Porter et al., Langmuir, 14, 7378-7386 (1998)(attachment of disulfides to gold); Son et al., J. Phys. Chem., 98,8488-93 (1994) (attachment of nitriles to gold and silver); Steiner etal., Langmuir, 8, 2771-7 (1992) (attachment of nitriles to gold andcopper); Solomun et al., J. Phys. Chem., 95, 10041-9 (1991) (attachmentof nitriles to gold); Solomun et al., Ber. Bunsen-Ges. Phys. Chem., 95,95-8 (1991) (attachment of nitriles to gold); Henderson et al., Inorg.Chim. Acta, 242, 115-24 (1996) (attachment of isonitriles to gold); Hucet al., J. Phys. Chem. B, 103, 10489-10495 (1999) (attachment ofisonitriles to gold); Hickman et al., Langmuir, 8, 357-9 (1992)(attachment of isonitriles to platinum); Steiner et al., Langmuir, 8,90-4 (1992) (attachment of amines and phospines to gold and attachmentof amines to copper); Mayya et al., J. Phys. Chem. B, 101, 9790-9793(1997) (attachment of amines to gold and silver); Chen et al., Langmuir,15, 1075-1082 (1999) (attachment of carboxylates to gold); Tao, J. Am.Chem. Soc., 115, 4350-4358 (1993) (attachment of carboxylates to copperand silver); Laibinis et al., J. Am. Chem. Soc., 114, 1990-5 (1992)(attachment of thiols to silver and copper); Laibinis et al., Langmuir,7, 3167-73 (1991) (attachment of thiols to silver); Fenter et al.,Langmuir, 7, 2013-16 (1991) (attachment of thiols to silver); Chang etal., Am. Chem. Soc., 116, 6792-805 (1994) (attachment of thiols tosilver); Li et al., J. Phys. Chem., 98, 11751-5 (1994) (attachment ofthiols to silver); Li et al., Report, 24 pp (1994) (attachment of thiolsto silver); Tarlov et al., U.S. Pat. No. 5,942,397 (attachment of thiolsto silver and copper); Waldeck, et al., PCT application WO/99/48682(attachment of thiols to silver and copper); Gui et al., Langmuir, 7,955-63 (1991) (attachment of thiols to silver); Walczak et al., J. Am.Chem. Soc., 113, 2370-8 (1991) (attachment of thiols to silver);Sangiorgi et al., Gazz. Chim. Ital., 111, 99-102 (1981) (attachment ofamines to copper); Magallon et al., Book of Abstracts, 215th ACSNational Meeting, Dallas, Mar. 29-Apr. 2, 1998, COLL-048 (attachment ofamines to copper); Patil et al., Langmuir, 14, 2707-2711 (1998)(attachment of amines to silver); Sastry et al., J. Phys. Chem. B, 101,4954-4958 (1997) (attachment of amines to silver); Bansal et al., J.Phys. Chem. B. 102, 4058-4060 (1998) (attachment of alkyl lithium tosilicon); Bansal et al., J. Phys. Chem. B, 102, 1067-1070 (1998)(attachment of alkyl lithium to silicon); Chidsey, Book of Abstracts,214th ACS National Meeting, Las Vegas, Nev., Sep. 7-11, 1997, I&EC-027(attachment of alkyl lithium to silicon); Song, J. H., Thesis,University of California at San Diego (1998) (attachment of alkyllithium to silicon dioxide); Meyer et al., J. Am. Chem. Soc., 110,4914-18 (1988) (attachment of amines to semiconductors); Brazdil et al.J. Phys. Chem., 85, 1005-14 (1981) (attachment of amines tosemiconductors); James et al., Langmuir, 14, 741-744 (1998) (attachmentof proteins and peptides to glass); Bernard et al., Langmuir, 14,2225-2229 (1998) (attachment of proteins to glass, polystyrene, gold,silver and silicon wafers); Pereira et al., J. Mater. Chem., 10, 259(2000) (attachment of silazanes to SiO₂); Pereira et al., J. Mater.Chem., 10, 259 (2000) (attachment of silazanes to SiO₂); Dammel,Diazonaphthoquinone Based Resists (1st ed., SPIE Optical EngineeringPress, Bellingham, Wash., 1993) (attachment of silazanes to SiO₂);Anwander et al., J. Phys. Chem. B, 104, 3532 (2000) (attachment ofsilazanes to SiO₂); Slavov et al., J. Phys. Chem., 104, 983 (2000)(attachment of silazanes to SiO₂).

Substrates to be Patterned

Substrates suitable for use in methods disclosed herein include, but arenot limited to, metals, alloys, composites, crystalline materials,amorphous materials, conductors, semiconductors, optics, fibers,inorganic materials, glasses, ceramics (e.g., metal oxides, metalnitrides, metal silicides, and combinations thereof), zeolites,polymers, plastics, organic materials, minerals, biomaterials, livingtissue, bone, films thereof, thin films thereof, laminates thereof,foils thereof, composites thereof, and combinations thereof. A substratecan comprise a semiconductor such as, but not limited to: crystallinesilicon, polycrystalline silicon, amorphous silicon, p-doped silicon,n-doped silicon, silicon oxide, silicon germanium, germanium, galliumarsenide, gallium arsenide phosphide, indium tin oxide, and combinationsthereof. A substrate can comprise a glass such as, but not limited to,undoped silica glass (SiO₂), fluorinated silica glass, borosilicateglass, borophosphorosilicate glass, organosilicate glass, porousorganosilicate glass, and combinations thereof. The substrate can be anon-planar substrate, such as pyrolytic carbon, reinforced carbon-carboncomposite, a carbon phenolic resin, and the like, and combinationsthereof. A substrate can comprise a ceramic such as, but not limited to,silicon carbide, hydrogenated silicon carbide, silicon nitride, siliconcarbonitride, silicon oxynitride, silicon oxycarbide, high-temperaturereusable surface insulation, fibrous refractory composite insulationtiles, toughened unipiece fibrous insulation, low-temperature reusablesurface insulation, advanced reusable surface insulation, andcombinations thereof. A substrate can comprise a flexible material, suchas, but not limited to: a plastic, a metal, a composite thereof, alaminate thereof, a thin film thereof, a foil thereof, and combinationsthereof.

Leveling of the Tip Array and Deposition of Patterning Composition ontoSubstrate Surface

The disclosed methods provide the ability for in situ imagingcapabilities, similar to scanning probe microscope-based lithographymethods (e.g., dip pen lithography) as well as the ability to pattern afeature in a fast fashion, similar to micro-contact printing. Thefeatures that can be patterned range from sub-100 nm to 1 mm in size orgreater, and can be controlled by altering the contacting time and/orthe contacting pressure of the tip array. Similar to DPN, the amount ofpatterning composition (as measured by feature size) deposited onto asubstrate surface is proportional to the contacting time, specifically asquare root correlation with contacting time, see FIG. 6. Unlike DPN,the contacting pressure of the tip array can be used to modify theamount of patterning composition that can be deposited onto thesubstrate surface. The pressure of the contact can be controlled by thez-piezo of a piezo scanner, see FIG. 2B. The more pressure (or force)exerted on the tip array, the larger the feature size. Thus, anycombination of contacting time and contacting force/pressure can providea means for the formation of a feature size from about 30 nm to about 1mm or greater. The ability to prepare features of such a wide range ofsizes and in a “direct writing” or in situ manner in milliseconds makesthe disclosed lithography method adaptable to a host of lithographyapplications, including electronics (e.g., patterning circuits) andbiotechnology (e.g., arraying targets for biological assays). Thecontacting pressure of the tip array can be about 10 MPa to about 300MPa.

At very low contact pressures, such as pressures of about 0.01 to about0.1 g/cm² for the preferred materials described herein, the feature sizeof the resulting indicia is independent of the contacting pressure,which allows for one to level the tip array on the substrate surfacewithout changing the feature size of the indicia. Such low pressures areachievable by 0.5 μm or less extensions of the z-piezo of a piezoscanner to which a tip array is mounted, and pressures of about 0.01g/cm² to about 0.1 g/cm² can be applied by z-piezo extensions of lessthan 0.5 μm. This “buffering” pressure range allows one to manipulatethe tip array, substrate, or both to make initial contact between tipsand substrate surface without compressing the tips, and then using thedegree of compression of tips (observed by changes in reflection oflight off the inside surfaces of the tips) to achieve a uniform degreeof contact between tips and substrate surface. This leveling ability isimportant, as non-uniform contact of the tips of the tip array can leadto non-uniform indicia. Given the large number of tips of the tip array(e.g., 11 million in an example provided herein) and their small size,as a practical matter it may be difficult or impossible to knowdefinitively if all of the tips are in contact with the surface. Forexample, a defect in a tip or the substrate surface, or an irregularityin a substrate surface, may result in a single tip not making contactwhile all other tips are in uniform contact. Thus, the disclosed methodsprovide for at least substantially all of the tips to be in contact withthe substrate surface (e.g., to the extent detectable). For example, atleast 90%, at least 95%, at least 96%, at least 97%, at least 98%, or atleast 99% of the tips will be in contact with the substrate surface.

The leveling of the tip array and substrate surface with respect to oneanother can be assisted by the fact that with a transparent, or at leasttranslucent, tip array and common substrate arrangement, one can observethe change in reflection of light that is directed from the top of thetip array (i.e., behind the base of the tips and common substrate)through to the substrate surface. The intensity of light reflected fromthe tips of the tip array gets greater upon contact with the substratesurface (e.g., the internal surfaces of the tip array reflect lightdifferently upon contact). By observing the change in reflection oflight at each tip, one can adjust the tip array and/or the substratesurface to effect contact of substantially all or all of the tips of thetip array to the substrate surface. Thus, the tip array and commonsubstrate preferably are translucent or transparent to allow forobserving the change in light reflection of the tips upon contact withthe substrate surface. Likewise, any rigid backing material to which thetip array is mounted is also preferably at least transparent ortranslucent.

The contacting time for the tips can be from about 0.001 s to about 60s, depending upon the amount of patterning composition desired in anyspecific point on a substrate surface. The contacting force can becontrolled by altering the z-piezo of the piezo scanner or by othermeans that allow for controlled application of force across the tiparray.

The substrate surface can be contacted with a tip array a plurality oftimes, wherein the tip array, the substrate surface or both move toallow for different portions of the substrate surface to be contacted.The time and pressure of each contacting step can be the same ordifferent, depending upon the desired pattern. The shape of the indiciaor patterns has no practical limitation, and can include dots, lines(e.g., straight or curved, formed from individual dots or continuously),a preselected pattern, or any combination thereof.

The indicia resulting from the disclosed methods have a high degree ofsameness, and thus are uniform or substantially uniform in size, andpreferably also in shape. The individual indicia feature size (e.g., adot or line width) is highly uniform, for example within a tolerance ofabout 5%, or about 1%, or about 0.5%. The tolerance can be about 0.9%,about 0.8%, about 0.7%, about 0.6%, about 0.4%, about 0.3%, about 0.2%,or about 0.1%. Non-uniformity of feature size and/or shape can lead toroughness of indicia that can be undesirable for sub-micron typepatterning.

The feature size can be about 10 nm to about 1 mm, about 10 nm to about500 μm, about 10 nm to about 100 μm, about 50 nm to about 100 μm, about50 nm to about 50 μm, about 50 nm to about 10 μm, about 50 nm to about 5μm, or about 50 nm to about 1 μm. Features sizes can be less than 1 μm,less than about 900 nm, less than about 800 nm, less than about 700 nm,less than about 600 nm, less than about 500 nm, less than about 400 nm,less than about 300 nm, less than about 200 nm, less than about 100 nm,or less than about 90 nm.

Examples Fabrication of Masters of Polymer Pen Arrays:

Shipley1805 (MicroChem, Inc.) photoresist was spin-coated onto gold thinfilm substrates (10 nm Cr adhesion layer with 100 nm of Au thermallyevaporated on a pre-cleaned oxidized Si <100> wafer). Square well arrayswere fabricated by photolithography using a chrome mask. The photoresistpatterns were developed in an MF319 developing solution (MicroChem,Inc.), and then exposed to O₂ plasma for 30 s (200 mTorr) to remove theresidual organic layer. Subsequently, the substrates were placed in gold(Type TFA, Transene) and chromium (Type 1020, Transene) etchingsolutions, respectively. Copious rinsing with MiliQ water was requiredafter each etching step to clean the surface. The photoresist was thenwashed away with acetone to expose the gold pattern. The gold patternedsubstrate was placed in a KOH etching solution (30% KOH in H₂O:IPA (4:1v/v)) at 75° C. for ˜25 min with vigorous stirring. The uncovered areasof the Si wafer were etched anisotropically, resulting in the formationof recessed pyramids. The remaining Au and Cr layers were removed by wetchemical etching. Finally, the pyramid master was modified with1H,1H,2H,2H-perfluorodecyltrichlorosilane (Gelest, Inc.) by gas phasesilanization.

Fabrication of Polymer Pen Array:

Hard PDMS (h-PDMS) (1,2) was used for fabricating the polymer penarrays. The h-PDMS was composed of 3.4 g of vinyl-compound-richprepolymer (VDT-731, Gelest) and 1.0 g of hydrosilane-rich crosslinker(HMS-301). Preparation of polymers typically required the addition of 20ppm w/w platinum catalyst to the vinyl fraction(platinumdivinyltetramethyldisiloxane complex in xylene, SIP 6831.1Gelest) and 0.1% w/w modulator to the mixture(2,4,6,8-tetramethyltetravinylcyclotetrasiloxane, Fluka). The mixturewas stirred, degassed, and poured on top of the polymer pen arraymaster. A pre-cleaned glass slide (VWR, Inc.) was then placed on top ofthe elastomer array and the whole assembly was cured at 70° C.overnight. The polymer pen array was carefully separated from thepyramid master and then used for lithography experiments. The procedurefor preparing the pen arrays is shown in FIG. 1A.

Patterning of Protein Arrays by Polymer Pen Lithography:

Tetramethylrhodamine 5-(and-6)-isothiocyanate (TRITC) conjugatedanti-mouse IgG arrays were generated on a Codelink™ glass slide (GEHealthcare) by Polymer Pen Lithography. In a typical experiment, thepolymer pen array was modified with polyethylene glycol silane(PEG-silane) to minimize non-specific interactions between the proteinand PDMS surface. To effect surface modification, the polymer pen arraywas briefly exposed to an oxygen plasma (30 sec) to render the surfacehydrophilic. Subsequently, it was immersed in a 1 mM aqueous solution ofPEG-silane (pH 2, MW 2,000, Rapp Polymere, Germany) for 2 hr, cleanedwith deionized water, and then blown dry with N₂. An aqueous solutionconsisting of 50 mg/ml glycerol and 5 mg/ml TRITC conjugated IgG wasthen spincoated onto the PEG-silane modified polymer pen array (1,000rpm for 2 min), and the pen array was used to generate protein arrays onCodelink™ slides. The pen array was leveled by monitoring the tip arraythrough the glass slide support. When a tip made contact with thesubstrate surface, the amount of light reflected from the tip increasedsignificantly, allowing for easy monitoring of when all or a substantialnumber of the tips were in contact with the substrate surface (e.g.,when the tip array was “leveled”). The patterning environment wasmaintained at 20° C. and 70% relative humidity. After the Polymer PenLithography process, the Codelink™ slide was incubated in a humiditychamber overnight, and rinsed with 0.02% sodium dodecyl sulfate toremove physisorbed material. FIG. 7 shows the fluorescent image of theas generated 3×3 IgG arrays. Each IgG dot was made by contacting the tiparray with the substrate for 3 seconds. The size of each IgG dot was4±0.7 μm.

The foregoing describes and exemplifies the invention but is notintended to limit the invention defined by the claims which follow. Allof the methods disclosed and claimed herein can be made and executedwithout undue experimentation in light of the present disclosure. Whilethe materials and methods of this invention have been described in termsof specific embodiments, it will be apparent to those of skill in theart that variations may be applied to the materials and/or methods andin the steps or in the sequence of steps of the methods described hereinwithout departing from the concept, spirit and scope of the invention.More specifically, it will be apparent that certain agents which areboth chemically and physiologically related may be substituted for theagents described herein while the same or similar results would beachieved.

All patents, publications and references cited herein are hereby fullyincorporated by reference. In case of conflict between the presentdisclosure and incorporated patents, publications and references, thepresent disclosure should control.

REFERENCES

-   1. C. A. Mirkin, ACS Nano 1, 79 (2007).-   2. K. Salaita, et al., Nat. Nanotech. 2, 145 (2007).-   3. D. S. Ginger, et al., Angew. Chem. Int. Ed. 43, 30 (2004).-   4. Y. Xia, G. M. Whitesides, Angew. Chem. Int. Ed. 37, 551 (1998).-   5. Y. Xia, G. M. Whitesides, Ann. Rev. Mater. Sci. 28, 153 (1998).-   6. M. Qi et al., Nature 429, 538 (2004).-   7. T. Ito, S. Okazaki, Nature 406, 1027 (2000).-   8. Y. L. Loo, et al., J. Am. Chem. Soc. 124, 7654 (2002).-   9. Z. Zheng, et al., J. Am. Chem. Soc. 128, 7730 (2006).-   10. A. Kumar, G. M. Whitesides, Appl. Phys. Lett. 63, 2002 (1993).-   11. M. N. Yousaf, et al., Proc. Natl. Acad. Sci. 98, 5992 (2001).-   12. S. Y. Chou, et al., Science 272, 85 (1996).-   13. S. Xu, et al., Langmuir 15, 7244 (1999).-   14. M. Geissler, Y. Xia, Adv. Mater. 16, 1249 (2004).-   15. B. D. Gates et al., Chem. Rev. 105, 1171 (2005).-   16. R. D. Piner, et al., Science 283, 661 (1999).-   17. S. Kramer, et al., Chem. Rev. 103, 4367 (2003).-   18. R. Maoz, et al., Adv. Mater. 11, 55 (1999).-   19. S. Lenhert, et al., Small 3, 71 (2007).-   20. K. Salaita et al., Angew. Chem. Int. Ed. 45, 7220 (2006).-   21. S. Hong, C. A. Mirkin, Science 288, 1808 (2000).-   22. L. M. Demers et al., Science 296, 1836 (2002).-   23. K.-B. Lee, et al., Science 295, 1702 (2002).-   24. For instance, DPN fabrication of a 10 μm×10 μm MHA feature on a    gold substrate with a conventional Si₃N₄ cantilever (radius of    curvature=20-60 nm) takes approximately 30 minutes.-   25. E. Delamarche et al., Langmuir 19, 8749 (2003).-   26. T. W. Odom, et al., Langmuir 18, 5314 (2002).-   27. H. Zhang, et al., Nano Lett. 4, 1649 (2004).-   28. X. Wang et al., Langmuir 19, 8951 (2003).

1.-28. (canceled)
 29. A tip array comprising a plurality of tips fixedto a common substrate layer, the tips and common substrate layer formedfrom an elastomeric polymer, the elastomeric polymer of the tipscomprising a thermoplastic polymer, a silicone polymer, or an epoxypolymer, each tip having a radius of curvature of less than about 1 μm,and the plurality of tips, common substrate, and rigid support togetherare at least transparent.
 30. The tip array of claim 29, wherein eachtip has a radius of curvature of less than about 0.5 μm.
 31. The tiparray of claim 30, wherein each tip has a radius of curvature of lessthan about 100 nm.
 32. The tip array of claim 29, wherein the tips arearranged in a regular periodic pattern.
 33. The tip array of claim 29,wherein the tips are identically-shaped.
 34. The tip array of claim 29,wherein the tips are pyramidal.
 35. The tip array of claim 29, whereinthe thickness of the common substrate layer is about 50 μm to about 100μm. 36.-37. (canceled)
 38. The tip array of claim 29, wherein the commonsubstrate layer and tips have a combined thickness of less than about200 μm.
 39. The tip array of claim 38, wherein the combined thickness isless than about 150 μm.
 40. The tip array of claim 39, wherein thecombined thickness is about 100 μm. 41.-45. (canceled)
 46. The tip arrayof claim 29, wherein the elastomeric polymer comprises a siliconepolymer.
 47. The tip array of claim 29, wherein the elastomeric polymeris modified by exposure to oxygen plasma.
 48. The tip array of claim 29,wherein the elastomeric polymer is modified by exposure to an oxidizer.49. The tip array of claim 29, wherein the elastomeric polymer comprisespolyethylene, polystyrene, polybutadiene, polyurethane, polyisoprene,polyacrylic rubber, fluorosilicone rubber, or a fluoroelastomer.